Lens sheets in which convex lenses are arrayed to intersect with one another according to prior arts are common to have basic configuration and principle in that printed patterns arrayed in the same way as the convex lenses are formed at a predetermined focal distance which forms thickness of the sheet and a Moire image is formed three-dimensionally according to the array density of the printed patterns (intervals of the patterns).
Korean Utility Model Registration No. 20-0311905 (granted on Apr. 17, 2003) discloses a ‘stereoscopically printed sheet of radial convex lenses’. Korean Utility Model Registration No. 20-0311905 proposes a stereoscopically printing method by a convex lens sheet to make a user see through by differentially dividing clear stereoscopic combined images and images from which unnecessary Moire is removed using a difference in levels of combined images formed at a focal distance and at a defocus distance. However, the stereoscopically printed sheet according to the prior art has a disadvantage in that it is difficult to manufacture high-quality products of a high gloss due to the dull matt surface of the sheet because of diffused reflection of the convex lenses which show within the limit of the focal distance.
Korean Patent No. 10-0841438 (granted on Mar. 9, 2006) discloses a ‘plane lens sheet using light transmission rate difference’ which can secure a focal distance by evenly coating refractive resin on the surfaces of convex lenses in order to express stereoscopic images.
Korean Utility Model Registration No. 20-0470351 (granted on Dec. 4, 2013) discloses a ‘three-dimensional sheet’. The three-dimensional sheet includes convex lenses of two types which are different from each other in size and radius of curvature, wherein small lenses are arrayed between array spaces of large lenses at the same angle and intervals to have different focal distances, so that three-dimensional images shown on the large lenses disappear but new three-dimensional images are formed by the small lenses when water or liquid is coated on the surfaces of the lenses. However, the three-dimensional sheet according to the prior art has a disadvantage in that image quality is somewhat poor.
Therefore, differently from the methods proposed by the prior arts, the present invention is to show differentiated images.